Altruism is a key concept in the design of decentralized systems with high survivability. We focus on a community of vampire bats to reveal how intra-group altruism produces group-wide survivability. Although these bats die within three days if food is unavailable, they can survive for over 10 years by developing a highly sophisticated social community in which they share food. This food-sharing behavior occurs not only among blood relatives, but also among unrelated individuals through self-organizing social relationships based on grooming behavior. We propose a simple network model that focuses on the relationship between food sharing and grooming. We performed simulations under periodic, stationary, and irregular feeding environments, and found that suitable update rules for social relationships depend on the type of environment. Our findings provide insights into how decentralized systems with high survivability can be designed based on altruism.

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